Heretofore strip chart recorders required that the operator set the pen by hand to a desired starting point on the chart for each separate scan, the usual starting point being with the pen on a major grid line of the chart. Despite some attempts to facilitate setting to a major grid line by hardware means such as provision of special perforations or other indexing means in the chart paper or by indexing devices on the chart drive mechanism, automatic indexing still was hard to initially set, required special paper or was limited to particular chart positions rather than to any major grid line. Such systems provided no simple means of readjustment in the event the chart paper expanded or shrank as a result of humidity changes.
It is an objective of our invention to provide microprocessor means which, among other duties, is responsible for the control of the chart drive; to automatically position the chart so that the pen is on a major grid line.
It is further an objective to make the above action take place by the depression of a single key switch by the operator.
It is a further objective to make a simple initialization step at the time of power turn-on the only time the operator must set the pen manually on a grid line.
Yet a further objective is to provide opportunity for equally simple reinitialization in the event that chart damage, removal, shrinkage or expansion due to humidity changes or other abnormal occurrences vitiate the original initialization.